This invention relates to methods and apparatus for beneficiating crushed or granulated ores, and particularly to techniques for separating valuable minerals such as coal from less valuable ash, sand, clay or fine rock fragments.
In the Appalachian coalfields, conventional coal mining operations have traditionally refined useful coal by washing from it less valuable ash, sand and clay, although fine particles of coal are often agglomerated with these residues produced by coal washing processes. Throughout the coalfields, so-called "gob piles" and coal slurry ponds of residues that have accumulated adjacent to coal washing yards, comprising stock piles rich in fine particles of useful coal which have proved to be economically impractical to recover.
Various techniques have been proposed for recovering mineral fines from such crushed ores, such as the eccentric weight vibrators of U.S. Pat. Nos. 4,240,903; 4,267,046; 4,184,965; 4,039,456 and 3,997,436; the pneumo-hydraulic vibrators of U.S. Pat. Nos. 4,070,275; 4,088,716 and 4,060,481; and the Westinghouse Electric Corporation "Electrical Coagulation" techniques described in Coal Mining & Processing, September 1982, pp. 64-67. These proposals are not believed to have achieved significant commercial success.